I've been silently following this debate in the forum for some time, but have only now taken the decision to wade in. Principally i'm worried that we are treating power supply and demand as a purely scalar problem. What I mean by that is everyone has this assumption that provided supply can be matched to demand at all points in time, with a good safety margin, all will be fine. Thus the discussion of the huge expansion of wind farms boils down to a discussion about net and peak power supply and windspeeds and efficiencies of windmills etc. This 'angle' is easy for windfarm supporters to twist, because any lack in demand can simply be made up for by yet more windfarms in lots of different places.
Really, we need to look at it in a more fundamental way. I too am suprised at the lack of power engineers participating. What we really need is a cynical w*nker who came up on an apprenticeship through CEGB about thirty years ago. Someone with knowledge of how stuff used to be in the 'good old days', and somebody able to distinguish between the various newly announced methods of turning mud into gold. Kindof a Richard North in the electrical industry.
I'm in communications engineering research [not power engineering], and my total industrial experience adds up to about 40 weeks over a series of placements. Therefore you need to take some of this stuff with a shovel-full of salt. However, whether you deal in picoWatts or Gigawatts on a daily basis, Maxwell's Equations are still the same and so certain principles are transferable.
The first thing that needs to be understood is that the mathematics of electricity supply and distribution is complex. That's not a cliche; I mean 'complex' in the formal mathematical sense. Voltages and Currents on national grid power lines approximate sine waves, and so have amplitudes and relative phase differences at a constant frequency. This is rather different to the 'batteries n lightbulbs' approach with DC electricity.
In the 'batteries n lightbulbs' approach, the wires between the two can be considered to be purely resistive. Resistance is a 'real' quantity.
However, for a network the size of the national grid, you have to take account of the inductance and capacitance of the circuit elements as well, referred to as reactance. Reactance is still measured in Ohms, but it is a 'complex' quantity.
Therefore, the total impedance (complex) of an element of the national grid = resistance (real) + reactance (imaginary), measured in Ohms.
I don't want to get bogged down in the maths of complex numbers, but time spent on Wikipedia will show you that it's not all that hard. The real-life implication of this complex impedance is that reactances in the network cause the voltage and current waveforms to either lag or lead each other.
Simply stated; reactive power is unusable power associated with energy STORED in the network. Resistive power is associated with energy dissipated in the network, and that used at the destination.
That means that reactive power has to be considered in keeping an electrical network up and running, and balanced out where appropriate.
Big industrial companies are actually billed for the amount of reactive power they introduce to the network; it's an extra line on their electricity bill. The reason is that electricity companies rightly consider it to be the responsibility of the user to balance the power factor of their network before connecting it to the grid. Otherwise, you get these reactive power components which are considered a waste, because they cause more current to flow in the line than if they had been cancelled out.
I suppose, relating to wind farms, the point is that your supply network is going to be much more spread out and thus introduce much more reactive load to the network per W of windfarm, than if the network was just going straight to a nuke or coal plant. Not only is it a matter of who pays for the lines to remote areas in the first place, but who pays for the ongoing cost of balancing the power factor? Or is this inbuilt at the windfarm side?
What would be useful now is for a national grid engineer to come out of the woodwork.
More importantly, i suppose this backs up Richard's point re: food industry. Years ago, there would have been an entire technical bureacracy dedicated to researching and 'knowing' all this stuff. They would have presented policy options to the politicians and would have had the final say in whether or not they were practical. Now we just seem to have a weird bog of EU, power suppliers, the grid, politicians, and assorted tranzies. The EU, politicians and tranzies are simply sticking with their 'scalar' 'batteries n lightbulbs' analysis, formulating policy on the basis of that, and then giving it to the industry to chew on.